In a field of electronic measurement and control involved in a working process of an electronic, electrical or intelligent product, whether a bidirectional interface device in and outside an existing Central Processing Unit (CPU) or Micro Control Unit (MCU) is used for inputting or outputting when being practically operated is determined by a direction selection circuit through an outgoing control line, and a practical direction and applicability of a level conversion circuit during application are determined during manufacturing and production. For example, a Darlington driving device ULN2003 is used for outputting driving; a bus driver 74HC245 is required to be determined by a direction pin when being operated; various data selectors are used for inputting selection; various data allocators are used for outputting allocation; a photocoupler cannot be used for inputting if being designed for outputting in a practical application circuit, and on the contrary, cannot be used for outputting if being designed for inputting; and a Light-Emitting Diode (LED) driver has a constant current driving function.
An interface circuit or level conversion circuit in the related art has the following defects.
One, for a unidirectional interface circuit, after an application circuit is designed or manufactured, an input or output direction of the application circuit is determined, and it is very difficult to change the input or output direction during a practical application.
Two, for a bidirectional interface circuit, after an application circuit is designed or manufactured, an adapted port voltage or current range of the application circuit is determined, and it is very difficult to apply the application circuit to an environment with high-voltage input or a high-current driving requirement during a practical application.
Three, undiversified application of a signal acquisition or output driving circuit board card applied to a field of measurement and control is determined in a design process, and is unlikely to be changed during a practical application, and no corresponding board card is allowed to be added regardless of lack of a path of input or output and sufficient redundancy of board cards applied to the other direction, so that a circuit structure is complex, and cost is increased.
Four, when a measurement and control product is researched and developed, there always exist problems of lack of either input or output and the like when a manufactured board card is debugged on the spot, unless there is sufficient redundancy left regardless of cost, and at this moment, if modification of a hardware design and remanufacturing are required, a research and development period is obviously prolonged.
Five, after a board card product is shaped, if software function upgrading is required, there usually exists a problem of lack of an input or output port.
Six, on the same application board card, a corresponding input or output interface chip is usually required to be selected according to a measurement and control object, which further causes increase of research and development cost or inventory management cost of a production element.
Seven, a withstanding voltage value of an input port of an MCU or a CPU is limited not to be twice higher than a working voltage of an interface circuit or a level conversion circuit, which seriously influences an application range of the MCU or the CPU.
For a problem of application circuit performance reduction caused by an incapability of an interface circuit or a level conversion circuit in supporting conversion of an input or output interface in the related art, no effective solution has been provided yet.